Method and Apparatus for Ballast-Assisted Reconfiguration of a Variable-Draft Vessel

ABSTRACT

A method for reconfiguring the hull form of a reconfigurable variable-draft vessel having a side hull and a center hull. In a method in accordance with the illustrative embodiment of the present invention, ballasting and de-ballasting operations assist in the vertical translation of the center hull relative to the side hull.

STATEMENT OF RELATED CASES

This case claims priority of U.S. provisional patent application 60/710,049, which was filed on Aug. 22, 2005 and is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to sea-faring vessels. More particularly, the present invention relates to a vessel having a multiple, reconfigurable hulls and a variable draft.

BACKGROUND OF THE INVENTION

Vessel hulls have traditionally been optimized for use in either shallow water or in deep water. For example, to navigate shallow waters, a relatively flat hull is used to maximize displacement and minimize draft. On the other hand, vessels that operate in deep waters frequently have v-shaped hulls that provide deep draft for good seakeeping.

If a vessel is designed for use in shallow waters, its performance in deep waters will be compromised, and vice-versa. This has spurred the development of variable-draft vessels, which are designed to operate well in both shallow and deep waters.

As the name implies, a variable-draft vessel is capable of varying its draft to accommodate changes in water depth or mission requirements. A variable-draft vessel that is disclosed in U.S. Pat. No. 6,877,450 B2 is capable of reconfiguring its hull form to change draft. The vessel includes a flat, center hull that is coupled to two side or outer hulls. The center hull is vertically movable relative to the side hulls to vary draft.

According to the patent, the center hull can be moved above or below the waterline. When the center hull is above the waterline, all buoyancy is provided by the side hulls, and the vessel takes maximum draft. As the center hull dips below the waterline, it contributes to the buoyancy provided by the side hulls. As a consequence, vessel draft is reduced.

To move the center hull relative to the side hulls, a variety of lifting mechanisms can be used. Regardless of the specifics of the lifting mechanism, if all vertical translation of the center hull is performed using the lifting mechanism, the vessel will incur penalties of added weight, cost, and space allocation.

SUMMARY OF THE INVENTION

The present invention provides a way to reconfigure the hull form of a reconfigurable variable-draft vessel with reduced or no reliance on a lifting mechanism.

In a method in accordance with the illustrative embodiment of the present invention, ballasting and de-ballasting operations assist in the vertical translation of the center hull. Accomplishing at least some of the required vertical translation in this manner reduces the range-of-motion requirements on the lifting mechanism.

In some embodiments, the variable-draft vessel incorporates special, over-sized tanks for ballasting operations and possesses an ability to lock its hulls in position relative to one another.

A method in accordance with the present invention for reconfiguring a reconfigurable, variable-draft vessel having a side hull and a center hull comprises:

-   -   (1) adding ballast to the side hull;     -   (2) switching a state of coupling of the side hull and the         center hull; and     -   (3) de-ballasting the side hull.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a reconfigurable, variable-draft vessel in accordance with the illustrative embodiment of the present invention.

FIG. 2 depicts the vessel of FIG. 1 in a deep-draft mode configuration.

FIG. 3 depicts the vessel of FIG. 1 in a shallow-draft mode configuration.

FIG. 4 depicts a flow diagram of a method in accordance with the illustrative embodiment of the present invention.

FIGS. 5A-5C depict the reconfiguration of a variable-draft vessel from a shallow-draft mode configuration to a deep-draft mode configuration.

FIGS. 6A-6C depict the reconfiguration of a variable-draft vessel from a deep-draft mode configuration to a shallow-draft mode configuration.

DETAILED DESCRIPTION

FIG. 1 depicts re-configurable, variable-draft vessel 100 in accordance with the illustrative embodiment of the present invention. Vessel 100 includes side hulls 102, struts 104, sponson 106, and deck house 108. The deck house, which is also referred to as the center hull, incorporates a pilot house, and, internally, a (lower) deck for vehicles and an (upper) deck for passengers.

Vessel 100 has a lifting mechanism for moving the center hull 108 relative to side hulls 102. In the illustrative embodiment, four lifting mechanisms 110 are used, wherein two mechanisms are disposed on each side of center hull 102, one located aft and one located toward the stern.

In conjunction with lifting mechanism 110, center hull 108 can be placed in a state in which it is locked to side hulls 102 such that the center hull and side hulls move in unison. Also, center hull 108 can be decoupled from side hulls 102 via lifting mechanism 110 so that the center hull and side hulls can move independently of one another.

In the illustrative embodiment, lifting mechanism 110 comprises an arrangement of hydraulic cylinders, guides, and bearings, such as is described in co-pending application (Atty. Dkt. No. 711-090us), filed on even date herewith and incorporated by reference herein. Those skilled in the art, after reading the present disclosure, will be able to design and build lifting mechanisms suitable for use in conjunction with the present invention. The specific configuration of lifting mechanism 110 is not germane to an understanding of the present invention and, therefore, will not be described further.

Vessel 100 is capable of reconfiguring between deep-draft modes (i.e., catamaran and SWATH) and shallow-draft modes (i.e., barge and wet-deck). FIG. 2 depicts vessel 100 in a typical deep-draft mode, wherein bottom 212 of center hull 108 is disposed well above side hulls 102 and above the waterline WL. Since center hull 108 does not typically contact the water when vessel 100 is configured in a deep-draft mode, vessel 100 can travel at higher speeds or with improved sea keeping relative to a shallow-draft mode.

FIG. 3 depicts vessel 100 in a typical shallow-draft mode, wherein the bottom of side hulls 102 and bottom 212 of center hull 108 are substantially co-planar. In the shallow-draft mode configuration that is depicted in FIG. 3, a portion of side hulls 102 and center hull 108 are submerged. In the shallow-draft mode, vessel 100 can approach a shoreline to launch or recover vehicles and personnel (e.g., via ramp 314, etc.).

Vessel 100 maintains constant displacement while changing draft via vertical translation of upper hull 108. In particular, to reduce draft, center hull 108 is translated downward until it contacts the water. Once in contact with the water, center hull 108 displaces some of the weight that was being displaced by side hulls 102. Consequently, draft is reduced.

In accordance with the illustrative embodiment of the present invention, the activity of lifting mechanisms 110 is supplemented or replaced using a sequence of ballasting and de-ballasting operations of side hulls 102 and, in some embodiments, of center hull 108 as well. The specifics of ballasting and de-ballasting are not described herein since they are well known to those skilled in the art.

FIG. 4 depicts, via flow chart, method 400 for reconfiguring variable-draft vessel 100 using ballasting and de-ballasting operations. FIGS. 5A through 5C depict a simplified representation of the relevant portions of vessel 100 during reconfiguration from a shallow-draft mode configuration to a deep-draft mode configuration.

FIG. 5A depicts vessel 100 in the shallow-draft mode (see also, FIG. 3), wherein the bottom of side hulls 102 are substantially co-planar with bottom 212 of center hull 108.

Since, for this example, vessel 100 is being reconfigured from a shallow-draft mode configuration to a deep-draft mode configuration, query 402 of method 400 is answered in the negative and processing transfers to query 404. In accordance with query 404, if side hulls 102 and center hull 108 are not coupled, then processing transfers to operation 408. If, on the other hand, side hulls 102 and center hull 108 are coupled, then processing transfers to operation 406, wherein that state is switched (i.e., side hulls 102 and center hull 108 are decoupled). The decoupling (or coupling) operation is performed in conjunction with lifting mechanisms 110. After switching state at operation 406, processing proceeds to operation 408.

In accordance with operation 408 of method 400, ballast is added to side hulls 102. That is, water is added to oversized ballast tanks (not depicted) that are situated within side hulls 102. The increase in weight of side hulls 102 causes them to sink deeper into the water, as depicted in FIG. 5B. This sinking of side hulls 102 results in a change in their vertical position relative to center hull 108 since the side hulls 102 and center hull 108 are decoupled.

At operation 410, the state of “coupling” of side hulls 102 and center hull 108 is switched via lifting mechanism 110. In this case, the state changes from “decoupled” to “coupled.”

After completing this change-in-state, ballast is released from the ballast tanks at operation 412. This causes vessel 100 to seek a new, higher level in the water consistent with its reduced weight. Since side hulls 102 and center hull 108 are now coupled to one another, as side hulls 102 rise, the center hull 108 rises as well. As depicted in FIG. 5C, center hull 108 rises above the water for deep-draft operation.

FIGS. 6A through 6C depict a simplified representation of the relevant portions of vessel 100 during reconfiguration from a deep-draft mode configuration to a shallow-draft mode configuration.

FIG. 6A depicts vessel 100 in a typical deep-draft mode (see also, FIG. 2), wherein bottom 212 of center hull 108 is disposed well above side hulls 102 and above waterline WL.

Since, for this example, vessel 100 is being reconfigured from a deep-draft mode configuration to a shallow-draft mode configuration, query 402 is answered in the affirmative and processing transfers directly to operation 408. Note that since vessel 100 is in a deep-draft mode configuration such that center hull 108 is above waterline WL, the side hulls 102 and center hull 108 will necessarily be in a coupled and locked state.

In accordance with operation 408 of method 400, ballast is added to side hulls 102. The increase in weight of side hulls 102 causes them to sink deeper into the water. This is depicted in FIG. 6B. Since side hulls 102 are coupled to center hull 108, center hull 108 drops toward waterline WL as well. In other words, unlike the previous example, there is no change in the relative vertical positions of center hull 108 and side hulls 102. Water is added to the ballast tanks of side hulls 102 until center hull 108 enters the water.

At operation 410, the state of “coupling” of side hulls 102 and center hull 108 is switched via lifting mechanism 110. In this case, the state changes from “coupled” to “decoupled.”

After completing this change-in-state, side hulls 102 are fully de-ballasted at operation 412. This causes side hulls 102 to float at their shallowest draft. Since side hulls 102 and center hull 108 are decoupled, center hull 108 does not rise in response. As a consequence, at the end of operation 412, vessel 100 is substantially in a shallow-draft mode configuration, as depicted in FIG. 6C.

In some embodiments in which vessel 100 is reconfiguring from deep-draft mode configuration to shallow-draft mode configuration, optional operations 414 and 418 are conducted. These operations enable center hull 108 to be additionally lowered relative to side hulls 102.

At operation 414, ballast is added to a ballast tank (not depicted) within center hull 108. This causes the center hull to lower its position in the water relative to side hulls 102, since the hulls are decoupled. At operation 416, the state of “coupling” of side hulls 102 and center hull 108 is changed again (from decoupled to coupled). As desired, at operation 418, the ballast tanks in center hull 108 are de-ballasted, causing vessel 100 to rise.

Thus, by appropriately ballasting and de-ballasting, coupling and decoupling, center hull 108 can be repositioned relative to side hulls 102 to reconfigure vessel 100 without using lifting mechanisms 110.

It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc.

Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents. 

1. A method for reconfiguring a reconfigurable, variable-draft vessel having a side hull and a center hull, wherein the method comprises: (a) adding ballast to said side hull; (b) switching a state of coupling of said side hull and said center hull; and (c) de-ballasting said side hull.
 2. The method of claim 1 wherein said variable-draft vessel reconfigures from a shallow-draft state to a deep draft state, the method further comprising decoupling said side hull and said center hull before performing operation (a).
 3. The method of claim 1 wherein said variable-draft vessel reconfigures from a deep-draft mode to a shallow-draft mode, the method further comprising, after operation (c): (d) adding ballast to said center hull; and (e) couple said center hull and said side hull.
 4. The method of claim 3 further comprising, after operating (e): (f) de-ballasting said center hull.
 5. A method for reconfiguring a reconfigurable, variable-draft vessel having a side hull and a center hull comprising changing ballast.
 6. The method of claim 5 further comprising alternatively coupling and decoupling said center hull and said side hull.
 7. The method of claim 5 wherein a lifting mechanism is not used to change a relative position of said center hull and said side hull.
 8. A variable-draft vessel comprising: a center hull; a side hull; a mechanism for coupling and decoupling said center hull and said side hull, wherein, when decoupled, said center hull and said side hull can move independently of one another; and a ballast tank, wherein said ballast tank is disposed in said side hull.
 9. The variable-draft vessel of claim 8, further comprising a ballast tank in said center hull.
 10. The variable-draft vessel of claim 8, further comprising a lifting mechanism for changing the relative vertical position of said center hull and said side hull. 